Bridge for stringed instruments



Jan. 11, 1966 UNKEL ETAL 3,228,276

BRIDGE FOR STRINGED INSTRUMENTS Filed Aug. 18, 1964 INVENTOR5 E a an lin Ha u-t ee (LL United States Patent f 2 Claims. (21. 84-209) This invention concerns a bridge for stringed instruments, and, although not so restricted, will hereinafter be described with reference to its use on a horizontally strung piano.

According to the present invention there is provided a bridge across which a string of a stringed instrument may be stretched between two fixed abutments of the instrument, and deflecting means for deflecting the string in its inoperative stretched condition to increase the length of string between said fixed abutments and thus reduce or remove entirely the resistance to movement of the bridge offered by the string.

Preferably the deflecting means is disposed on the side of said bridge opposite to that nearest the sounding section of the string.

In a preferred embodiment the section of string between one of said fixed abutments and said deflecting means is coincident with the rectilinear line joining said fixed abutments, said section of string oscillating in both directions about said rectilinear line when in operation.

The deflecting means preferably comprises a bar fixed to the bridge and movable therewith. The bar is preferably adjustable relative to said bridge to vary the tension of said string.

The invention also includes a stringed instrument provided with the bridge and components set forth above.

The invention is illustrated, merely by way of example, in the accompanying diagrammatic drawings, in which:

FIGURE 1 is a part sectional elevation of part of a grand piano according to the present invention,

FIGURE 2 is a view, similar to FIGURE 1, of part of a conventional grand piano,

FIGURE 2a is a vibration diagram illustrating the wave form produced by the piano of FIGURE 2,

FIGURE 3 is a view of the device shown in FIGURE 1 illustrating its mode of operation, and

FIGURE 3a is a vibration diagram illustrating the wave form produced by the piano of FIGURES 1 and 3.

Referring to FIGURE 1, a grand piano comprises two fixed abutments A and B between which a string (or wire) S is stretched across a surface a of a bridge a. The bridge a is fixed on the upper surface of a resonance board b for vertical movement therewith. Two pins 6, d are provided on the bridge a for guiding the string S.

A deflector arm e is fixed to a lateral projection of bridge a by screws 1 whereby the deflector arm e may be adjusted relative to the bridge a. A recess g is provided between the lateral projection and the resonance board b.

The deflector arm e is adjusted relative to bridge a until the section S of string S between abutment A and point D on arm e is horizontal i.e. is coincident with the rectilinear line G between the abutments A and B. The surface al of bridge a slopes downwardly towards arm e and abutment A, as clearly seen in FIGURE 1 whereby the section S of string S which crosses surface a lies flat thereon, the section S being linear between point C on surface a and the deflector arm e.

The sounding section S of string S between point C and abutment B is also linear, and thus, in the inoperative,

3,228,276 Patented Jan. 11, 1966 tensioned position shown in FIGURE 1, the deflector arm e deflects the tensioned string S to form it into a slight S shape, thereby increasing the length of string between abutments A and B.

At points C and D three vertical forces P P and P act on bridge a. Forces P and P are due to the tension-ed string S and force F; is due to the elastic bending of resonance base b.

Referring now to FIGURE 2, it will be seen that the bridge according to the present invention (seen in FIG- URE l) differs therefrom by the provision of the deflector bar e and the lateral projection to which the bar e is fixed. The bridge a of the device of FIGURE 2 is symmetrical, being provided with a horizontal upper surface across which the string S is disposed when stretched between abutments A and B.

The mode of operation of the device of FIGURE 2 is illustrated in FIGURES 2 and 2a. When the string S vibrates the bridge a and resonance board b also vibrate. Downward movement of the bridge and resonance board is substantially unresisted apart from the resilience of board b itself, and these components move downwardly a distance r. The string S having a sounding portion S between the bridge a and abutment B, a portion 8.; on the surface of bridge a and a portion S between bridge a and abutment A assumes a position indicated by broken lines S in its lowermost position. Portions S and S move to position 8,, and S corresponding to the deflection r but sounding portion S moves to a portion S which corresponds to deflection r plus the oscillation amplitude corresponding to the free vibration of string portion S Vibration of sounding portion S of string S is indicated by the wave form in FIGURE 2a where the section below time axis Z indicates the lower vibration of string S. It will be seen that the amplitude of string portion S below the neutral position is A comprising the deflection r and a portion A corresponding to the amplitude of the free vibration of string portion 8,. The form of vibration of the bridge a and board b is indicated by R whose maximum amplitude is, of course, 1'.

After deflection to the lowermost position, the bridge a, board b and string S return to the neutral position shown in full lines in FIGURE 2 and should continue to an uppermost position defining the upper limit of the vibration. Portion S of string S does extend to position S the amplitude corresponding to the free vibration of portions S However, bridge a and board 11 are prevented from moving vertically upwardly past the neutral position shown to any appreciable extent due to the resistance to movement provided by the tensioned string S. Thus the maximum amplitude of S is A due solely to the free vibration of portion S the maximum amplitude thus being smaller than that of S by r.

Thus the resulting vibration of the sounding portion S of string S is not uniform, as clearly seen from FIG- URE 2a, and the sound produced thereby is consequently affected.

The restriction to upward movement of the bridge a, board [2 and string S is removed by the device according to the present invention. Thus the upward movement of these components is limited because the string S is under tension and is inextensible, by providing an additional length of string between abutments A and B, without affecting the tension of the string, the fault can be overcome.

Being fixed to bridge a, deflector arm e (FIGURES 1 and 3) moves therewith and thus, upon vertically upward movement of bridge a, arm e releases the tension in spring S, removing the resistance to upward movement of bridge a provided by the string, and thus permitting relatively free upward movement of bridge a and resonance board I). The upper limit of sounding portion S of string S is indicated by S the amplitude (A) of which is the sum of the amplitude A corresponding to the free vibration of portion S and r", being the distance by which bridge a and board [2 moves vertically upwardly. The lower limit of sounding portion S is indicated by S the amplitude (A) of which is the sum of the amplitude A corresponding to the free vibration of portion S and r, being the distance by which bridge a and board b move vertically downwardly.

By adjusting the position of deflector arm e, the amplitudes A and A can be made substantially equal, and thus the sounding string portion S will oscillate uniformly about the mean position. The sound produced by the device of FIGURES 1 and 3 will be softer and of better timbre than that produced on the conventional device of FIGURE 2.

The device can, of course, be modified in many aspects, e.g. the deflector arm 6 need not be fixed to bridge a but could be fixed to board I).

It will be appreciated that invention is applicable to any stringed instrument in which a bridge is employed.

We claim:

1. In a string instrument, the combination of a sounding board having a neutral position and adapted to oscillate in the direction upwardly and downwardly thereof when said string instrument is being played;

a first abutment and a second abutment spaced from said first abutment, both of said abutments being located in a common transversal plane;

a bridge carried by said sounding board for oscillation therewith and including a main portion leaving an abutment face and a projection projecting laterally from said bridge in the direction toward said second abutment and parallel to said sounding board with spacing therefrom, said projecting portion having an upper surface downwardly spaced from said abutment face of said main portions;

a string abutting said abutments and contacting only said abutment face of said main portion of the bridge; and deflecting means carried only by said projection of said bridge and operative to deflect said string in the region of said projection downwardly of said abutment face in the direction toward, but short of said upper surface of said projection so as to produce downward pressure of said string only on said abutment face of said main portion whereby, when said sounding board carrying said bridge oscillates upwardly of its neutral position upon said string instrument being played, said deflecting means will move upwardly with said bridge, thereby releasing said string and reducing said downward pressure on said bridge so that the latter is enabled to oscillate substantially freely.

2. In a string instrument, the combination of a sounding board having a neutral position and being adapted to oscillate upwardly and inwardly of said neutral position when said string instrument is being played, a first abutment and second abutment spaced from said first abutment, both of said abutments being located in a common transversal plane;

a string abutting said abutments and being tautly stretched therebetween;

a bridge carried by said sounding board and including a main portion having a lateral face facing said second abutment and an abutment face extending substantially parallel to said common plane, said abutment face having a first edge adjacent to said first abutment and projecting upwardly of said common plane by a given distance, and a second edge adjacent said second abutment and projecting upwardly of said common plane by a distance less than said given distance, said abutment face sloping from said first edge to said second edge and said string being supported on said abutment face, said bridge being further formed with a projection projecting from said lateral face toward said second abutment and having a lower face facing said sounding board with vertical spacing therefrom and an upper face downwardly spaced from said common plane;

and deflecting means carried by said projection and extending upwardly of said upper face thereof, said deflecting means normally deflecting said string downwardly toward, but short of said upper face when said string instrument is not being played, and said deflecting means moving upwardly when said bridge oscillates in upward direction during playing of said string instrument whereby said string is momentarily relaxed and resistance to upward oscillation of said bridge is removed, so that resistance of said string to oscillation of said bridge is thereby substantially removed.

FOREIGN PATENTS 242,178 11/1925 Great Britain.

LEO SMILQW, Primary Examiner. 

1. IN A STRING INSTRUMENT, THE COMBINATION OF A SOUNDING BOARD HAVING A NEUTRAL POSITION AND ADAPTED TO OSCILLATE IN THE DIRECTION UPWARDLY AND DOWNWARDLY THEREOF WHEN SAID STRING INSTRUMENT IS BEING PLAYED; A FIRST ABUTMENT AND A SECOND ABUTMENT SPACED FROM SAID FIRST ABUTMENT, BOTH OF SAID ABUTMENTS BEING LOCATED IN A COMMON TRANSVERSAL PLANE; A BRIDGE CARRIED BY SAID SOUNDING BOARD FOR OSCILLATION THEREWITH AND INCLUDING A MAIN PORTION LEAVING AN ABUTMENT FACE AND A PROJECTION PROJECTING LATERALLY FROM SAID BRIDGE IN THE DIRECTION TOWARD SAID SECOND ABUTMENT AND PARALLEL TO SAID SOUNDING BOARD WITH SPACING THEREFROM, SAID PROJECTING PORTION HAVING AN UPPER SURFACE DOWNWARDLY SPACED FROM SAID ABUTMENT FACE OF SAID MAIN PORTIONS; A STRING ABUTTING SAID ABUTMENTS AND CONTACTING ONLY SAID ABUTMENT FACE OF SAID MAIN PORTION OF THE BRIDGE; AND DEFLECTING MEANS CARRIED ONLY BY SAID PROJECTION OF SAID BRIDGE AND OPERATIVE TO DEFLECT SAID STRING IN THE REGION OF SAID PROJECTION DOWNWARDLY OF SAID ABUTMENT FACE IN THE DIRECTION TOWARD, BUT SHORT OF SAID UPPER SURFACE OF SAID PROJECTION SO AS TO PRODUCE DOWNWARD PRESSURE OF SAID STRING ONLY ON SAID ABUTMENT FACE OF SAID MAIN PORTION WHEREBY, WHEN SAID SOUNDING BOARD CARRYING SAID BRIDGE OSCILLATES UPWARDLY OF ITS NEUTRAL POSITION UPON SAID STRING INSTRUMENT BEING PLAYED, SAID DEFLECTING MEANS WILL MOVE UPWARDLY WITH SAID BRIDGE, THEREBY RELEASING SAID STRING AND REDUCING SAID DOWNWARD PRESSURE ON SAID BRIDGE SO THAT THE LATTER IS ENABLED TO OSCILLATE SUBSTANTIALLY FREELY. 